Zyxel NSA221 and Time Machine

macrumors newbie

I have a Zyxel NAS (NSA221), and a late 2011 MBP running Lion. I understand that there are multiple problems with Time Machine recognising a NAS, something to do with a changing of authentication. I can mount the drive and see it in Finder, but Time Machine doesn't detect it, can anyone assist?

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